Folau was shown a yellow card before being given a citing commissioner's warning following two separate incidents involving Ireland captain O'Mahony in Sydney, where the Six Nations champions won 20-16 to take the series 2-1.
The Australia full-back faced a World Rugby disciplinary hearing on Wednesday and was given a suspension that is set to rule him out of the Waratahs' Super Rugby clash with the Rebels on Friday.
Folau and Rugby Australia have until Friday morning to appeal against the decision.
